In this project we wish to obtain fundamental information about the myofibrillar-type proteins from cardiac, skeletal, and smooth muscles and from some cells that are not muscles. We will carry out comparative sequence studies on actins from normal human heart muscle and human blood platelets, as well as on actin from Acanthamoeba. Proposed work on myosin includes a study of the complete amino acid sequence of the heavy chain of rabbit skeletal muscle myosin and comparative sequence studies as well as physical studies on specific fragments of myosins from cardiac and smooth muscle. Other work on myosin includes sequence studies on the alkali and "DNTB" light chains of human cardiac myosin.